This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project addresses the intrinsic diversity among circulating populations of HIV-1 in various geographical locations and the need to develop vaccines that can elicit enduring protective immunity to variant HIV-1 strains. In the current project, we will test virus-like particle (VLP) immunogens that can optimize mucosal and systemic Env-specific immune responses for protection from heterologous SHIV challenge in rhesus macaques by vaginal exposure (the most common route of HIV-1 transmission worldwide). Each DNA plasmid expresses VLPs from SHIV gene sequences whereas each DNA construct expresses a non-infectious lentiviral VLP from a single DNA plasmid. Each VLP gene insert expresses the gag, pol, env, vpu, tat, and rev gene sequences that are expressed from a cytomegalovirus immediate-early promoter via plasmid DNA. Thus, VLP mRNA splicing and nuclear export will be controlled by viral mechanisms and translated proteins efficiently secrete VLPs from transfected cells. In this proposal, gene inserts expressing SHIV VLPs were expressed from DNA. In addition, SHIV VLPs were purified from the supernatant of primate cells transfected with the same DNA plasmids. Rhesus macaques were vaccinated in a prime/boost regimen (DNA prime/particle boost) for the elicitation of both humoral and cellular immunity, for eventual protection studies from heterologous clade B SHIV challenge [SIV162p3]. The goals of this proposal are to assess and compare the induction of immune responses between VLP immunogens with primary envelopes to the elicitation of immunity by VLP immunogens with an envelope representing the consensus envelope sequences (clade B or clade C). Immunization of 12 rhesus monkeys in groups of 4 were carried out. A control group of 4 monkeys received no vaccine.